Server does not come up after upgrading Couchbase Server Community Edition from 2.0.1 to 2.2.0

Hello,

I'm trying to do upgrade couchbase server community edition from 2.0.1 to 2.2.0 using below steps.

1. Take the backup of existing bucket using command
nohup /opt/couchbase/bin/cbbackup http://localhost:8091 /app/cache/bkup -u Administrator -p c0mcast! -b customerdb &
2. Stop the current couchbase server with version 2.0.1 using command
sudo /etc/init.d/couchbase-server stop
3. Upgrade the couchbase server using command
rpm -U ~/couchbase/couchbase-server-community_2.2.0_x86_64.rpm
4. Monitor while the server comes up using command
cbstats localhost:11210 warmup
However I could not go any further after the step 3 as the couchbase server could not be started after the upgrade.
It says the server is started but however I could not access the admin console using http:\localhost:8091.

I've run the cbcollect_info and uploaded the log data using below command.

curl --upload-file error_details.zip https://s3.amazonaws.com/customers.couchbase.com/cable.comcast/

Also attaching the same file for reference.

Any pointers to fix this would be very helpful to do the upgrade in higher environments.

Thanks,
Madhav